Add a reference to your project to the excel interop dll. To do this
on the .NET tab select
Microsoft.Office.Interop.Excel.
There could be multiple assemblies
with this name. Select the
appropriate for your Visual Studio
AND Excel version.

Here is a code sample to create a new Workbook and fill a column with
the items from your list.

using NsExcel = Microsoft.Office.Interop.Excel;
public void ListToExcel(List<string> list)
{
//start excel
NsExcel.ApplicationClass excapp = new Microsoft.Office.Interop.Excel.ApplicationClass();
//if you want to make excel visible
excapp.Visible = true;
//create a blank workbook
var workbook = excapp.Workbooks.Add(NsExcel.XlWBATemplate.xlWBATWorksheet);
//or open one - this is no pleasant, but yue're probably interested in the first parameter
string workbookPath = "C:\test.xls";
var workbook = excapp.Workbooks.Open(workbookPath,
0, false, 5, "", "", false, Excel.XlPlatform.xlWindows, "",
true, false, 0, true, false, false);
//Not done yet. You have to work on a specific sheet - note the cast
//You may not have any sheets at all. Then you have to add one with NsExcel.Worksheet.Add()
var sheet = (NsExcel.Worksheet)workbook.Sheets[1]; //indexing starts from 1
//do something usefull: you select now an individual cell
var range = sheet.get_Range("A1", "A1");
range.Value2 = "test"; //Value2 is not a typo
//now the list
string cellName;
int counter = 1;
foreach (var item in list)
{
cellName = "A" + counter.ToString();
var range = sheet.get_Range(cellName, cellName);
range.Value2 = item.ToString();
++counter;
}
//you've probably got the point by now, so a detailed explanation about workbook.SaveAs and workbook.Close is not necessary
//important: if you did not make excel visible terminating your application will terminate excel as well - I tested it
//but if you did it - to be honest - I don't know how to close the main excel window - maybee somewhere around excapp.Windows or excapp.ActiveWindow
}